1. Field of the Invention
The present invention relates to a method for avoiding or preventing contamination of an interior or inner surface of a hollow glass body with alkali compounds during thermal processing or working. The present invention also relates to a glass container produced by the method, especially to a glass container for medicinal purposes.
2. Description of the Related Art
Alkali compounds, especially alkali borates, evaporate during thermal processing of hollow glass bodies, especially during processing by flames and/or jet flames. These vapors are deposited on the surfaces of the hollow glass body to be processed. This alkali compound layer is a particular problem when containers for food or medicine are made from the hollow glass bodies. The chemical composition of the glass and/or glass surfaces is of great importance for these applications.
Glass tubing is the starting article for manufacture of glass containers for medicinal purposes, such as ampoules, bottles, cartridge ampoules, pens and syringes. Suitable glass tubing is commercially obtainable. The glass tubing is thermally cut to length. The bottoms that are produced in the glass tubing or tubes in this process are opened with heat. The thermal processing steps can be understood in the sense of after-working, since this method amounts to after-working of a finished rigid glass intermediate product for manufacture of the end product, i.e. the glass tube or tubing. Alkali compounds especially evaporate  during the thermal opening, and contaminate the interior of the glass tube and thus the container to be made from it.
The shaping of glass gobs into hollow glass bodies by glass blowing methods, in which a glass blower blows air into a hollow glass body, has been known since the beginning of the glass making arts according to Heinz G. Pfaende, in “Schott Glass Dictionary {Schott-Glaslexikon}”, Landsberg am Lech, MVG Verlag 1997.
DE 35 21 623 C2 teaches prevention of penetration of fine glass particles into the interior of a hollow soot cylinder produced by a directed glass flow. The required burners are constructed so that the penetrating glass particles are blown from the cylinder interior to the cylinder edge by the glass flow.
A process for cutting a glass tube to length from a continuous glass strand is described in DE 100 47 850 A1. In order to cut the glass strand to length without chips or splinters it is suggested that the desired cutting site should be heated and drawn. Then the glass strand is to be cut through at the desired cutting site. In order to avoid producing a low pressure in the tube during cooling, an air hole is produced in the tube during heating. This should happen at the same time as the cutting through. The hole is burned through by means of a laser, which should be immediately switched off after the hole burning operation, in order to reduce the formation of evaporated products and possible condensation in the tube. 